The present investigation was undertaken to examine the anticancer activity of the methanol extract from Houttuynia cordata on ICR mouse with induced abdominal cancer and L1210 cancer cells. When the methanol extract of Houttuynia cordata (10∼200 $mu extrm{g}$/$mell$) was administered orally to ICR mouse with abdominal cancer, 47.8% of the best life prolonging effect was obtained. In case of cytotoxicity study (inhibition of cell proliferation) of Houttuynia cordata extract against L1210 cells, $IC_{50}$/ was found to be 62.8 $mu extrm{g}$/$mell$. In contrast to such considerable toxicity against cancer cell line, the toxicity demonstrated by the identical extract against normal lymphocytes was very meagre as shown to be < 5% compared with 86.5% in case of L1210 cells at the same condition. To get an insight into the reaction mechanism undelying the anticancer activity, $O_2$ion quantity and antioxidant enzyme activities such as superoxide dismiutase (SOD) and glutathione peroxidase (GPx) of L1210 cells in the presence of Houttuynia cordata extract were measured. The increased values of SOD and GPx enzyme activities in addition to the augmented generation of $O_2$ ion in L1210 cells implied that the reactive oxygen species induding $O_2$ion which were presumably induced by Houttuynia cordata extract might have participated in the process of L1210 cells cytotoxicity.